In recent years there have been many documented cases in which very young children have been badly burnt as a result of using a live extension cord socket as a teething aid. It is known that the burns are caused by the electrical current running through the cord. In most cases, the victim of these burns has required reconstructive surgery to repair the damage to the facial area surrounding the mouth.
The mechanism of this type of burn has not been the subject of a great deal of research as most research has been directed to the devastating injuries which can be sustained at voltages much higher than the household voltage of 115 volts. It has been determined by experiments carried out by the present inventors that the major cause of the burns is by resistive heating caused in the tissues by an electric current running through the child's saliva that has come into electrical contact with the hot or live terminal of the socket.
Saliva is a relatively good conductor, but at the relatively low household voltage, it has been determined that it takes approximately seven to eight seconds before tissue necrosis occurs. It is thought that the electrical current causes tetany, or a sustained clamping of the jaws, which prevents the child from letting go until the saliva within the socket is heated and boiled away. Unfortunately this occurs after the child has been injured.
Prior safety devices include sliding sleeves that cover the socket slot. These are not effective because saliva may still get through the gaps. These devices, along with other devices that cover or enter the socket slot, require an overt action on the part of the user. In many cases they are easily removed and they provide no protection for the type of injury described above.